The present invention relates to an electric sewing machine and, more particularly, to an indication arrangement for use in the sewing machine for indicating a range of pitch of a cloth advance suited for the selected zig-zag pattern.
Recently, there have been proposed various types of electrically operated sewing machines which provide a number of patterns of zig-zag sewing. The patterns are basically determined by two factors which are: the lateral movement of the thread carrying needle; and the pitch of advance or retreat of the cloth effected between the two succeeding stitches. The first factor, that is, the lateral needle movement, is generally controlled by a cam which is selected from a number of different cams, while the second factor, that is, the pitch of advance of the cloth, is controlled by a suitable pitch adjusting means such as a dial incorporated in the sewing machine. In order to reproduce a prearranged pattern, it is necessary to select a proper cam and also to set the dial to a position which provides a proper pitch of advance of the cloth.
In the conventional sewing machine, the pitch control dial has an index marking which is, as the dial is turned, selectively brought in register with numerical markings scaled adjacent and around the dial. These markings, however, only assist the operator to understand the pitch of cloth advance with respect to the registered numerical marking. Therefore, in such conventional sewing machines, it is necessary for the operator to make several trials of sewing before the sewing pitch control dial is set to an optimum position, or otherwise the dial has to be set empirically by the operator.
Although there have been proposed a pitch control dial with a plurality of concentric bars indicating an available range for the different cams, this arrangement needs time to find one bar corresponding to the selected cam. Furthermore, the number of the bars becomes larger as the cams are increased.